1. Field of the Invention
The present invention relates to a hot water type heating apparatus for vehicles, which uses a flow control valve for controlling a flow of hot water.
2. Related Art
A conventional temperature control method for controlling temperature of supply air in an automotive air conditioner including a hot water type heating apparatus, includes controlling the temperature of supply air by controlling the flow of hot water to an heat-exchanger for heating. This method for the controlling flow quantity of hot water has the following advantages as compared to an air-mix type method for controlling temperature of supply air by controlling a mixture ratio between cool air and hot air with an air mix damper.
In the hot water flow quantity control method, a mixture space for mixing cool air and hot air, as in the air-mix type method is not required. Thus, it is possible to reduce the volume of the ventilating duct and reduce ventilating resistance by abolishing the mixture space, thereby reducing electric power and ventilating noise.
As a hot water flow quantity control device, a control valve for controlling the flow quantity of hot water integrated as a unit with a heat-exchanger for heating is disclosed in Japanese Patent Publication No. Sho 61-10327. In this device, a tank is provided at one end of tubes of the heat exchanger for heating to distribute and gather hot water toward the tubes, and another tank is provided at the other end of tubes to make hot water flow around a U-turn.
A control unit is disposed in the tank at the one end of the tubes and includes a hot water flow quantity control valve, hot water bypass circuit, a pressure valve operative in response to pressure for controlling the bypass circuit. Thus, the entire structure of the heating apparatus is simplified.
In this apparatus, all components are disposed in the tank at the one end of the tubes to simplify the structure; however, there are problems in practical use which are explained below.
Since the hot water flow quantity control valve and the pressure valve are disposed in the tank, the heat exchanger should be prepared specially for the individual apparatus. Thus, it is difficult to apply the heat exchanger to various types of apparatus. Specially, it is impossible to commonly apply the heat exchanger to both the hot water flow quantity control type for controlling temperature of supply air by using the hot water flow quantity control valve, and the air mixture type for controlling temperature of supply air by mixture ratio of cool air and hot air without using the hot water flow quantity control valve.
The above conventional apparatus can be applied only to the heat exchanger for heating in which the hot water flows around a U-turn, and cannot be applied to a type of heat exchanger in which the hot water flows in one direction from the one tank to the other tank.
Further, since the hot water flow quantity control valve and the pressure valve are disposed within the tank, it is difficult to maintain these valves.
The present invention is made in view of the above problems, and an object of the present invention is to provide a heating apparatus for vehicles in which a hot water flow quantity control valve integrated as a unit with a bypass circuit is disposed in a hot water pipe portion outside of a heat exchanger for heating.
Another object of the present invention is to provide a heating apparatus for vehicles which is capable of being assembled into a hot water pipe easily when the apparatus is mounted on the vehicle.